in situ immobilization of uranium in structured porous pacific … · 2005. 4. 27. · media via...
TRANSCRIPT
Concept/HypothesesConcept/Hypotheses
ORIGINAL HYPOTHESIS: “Radionuclides in low-permeability porous matrix regions of fractured saprolite can be effectively isolated and immobilized by stimulating localized in-situ
biological activity in highly-permeable fractured and microfractured zones within the saprolite.” (Roden and Scheibe, 2005)
Field Site DevelopmentField Site Development
• Geophysical wells GP-1, GP-2, GP-3, GP-4 and GP-5 were recently completed.
• Additional monitoring wells (blue in figure to the left) will be multi-level sampling (MLS) wells. Materials have been delivered and construction will begin soon.
• Site infrastructure will then be complete. Wells FW212, FW213, and FW214 will serve as electron donor injection wells; flush experiment (tracer and water injection) will be conducted using FW215.
In Situ Immobilization of Uranium in Structured Porous Media via Biomineralization at the Fracture/Matrix
Interface (FRC Area 2 Field Project)
The original hypothesis focused on the intact fractured saprolite zone
INTACT SAPROLITE HAS ISSUES:• Low U(VI) concentrations• High nitrate concentrations• Low permeability
REVISED HYPOTHESIS: “In heterogeneous porous media, microbial activity can be stimulated at interfaces between zones of high and low groundwater flow rates in such a
manner as to create a local, distributed redox barrier. Such a barrier will inhibit the transfer of contaminants from the low-flow zones that serve as long-term contaminant sources into the
high-flow zones that transport contaminants to receptors.”
BROMIDE MISSING AT GOVERNMENT NUCLEAR RESERVATION
Area 2 Tracer Test 10 Aug 04IC data through 22 Sep 04
0
20
40
60
80
100
120
140
0 10 20 30 40 50 60 70 80 90 100
Elapsed Time (h)
[Br]
-mg/
L - I
C
FW212
FW213FW214
FW216-1FW216-2
TPB16GW835
FW202-2
DP13
Seep1Seep2
Events
FW215 - Injection Well
0
100
200
300
400
500
0 200 400 600 800
Bromide breakthrough curves from the Area 2 tracer test conducted August 2004.
GRAVEL CAPTURES RESEARCHERS’ ATTENTION
Vertical profiles of total sediment-associated uranium at two boreholes in
Area 2. Gravel layer is at approximately 18 feet below ground surface.
Saprolitic Fill Material
Intact Saprolite Material
GravelZone
0.01.02.03.04.05.06.07.08.09.0
10.0
0 10 20 30 40 50 60
Time (d)
(mM
)
CH3CH2OHCH3COO-CH3CH2OHCH3COO
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 10 20 30 40 50 60
Time (d)
NO
3-, S
O42
- (m
M) NO3-
SO42-NO3SO4
0.02.04.06.08.0
10.012.014.016.018.020.0
0 10 20 30 40 50 60
Time (d)
Fe(II
) (m
mol
/L)
TotalDissolvedFe2TotFe2aq
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 10 20 30 40 50 60
Time (d)
CH4,
DIC
(mM
)
CH4CH4DICDIC
Terminal Electron Accepting Processes (TEAPs) –Experimental and Model Results
0.000.010.020.030.040.050.060.070.080.090.10
0 10 20 30 40 50 60
Time (d)
U(VI
) (m
mol
/L)
TotalUVITot
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0 10 20 30 40 50 60
Time (d)
U(VI
)aq
(uM
)
TotalUVIaq
U(VI) Partitioning and Reduction –Experimental and Model Results
cDNA clone library (Total clones 41)
Geobacter
Oxalobacter
Clostridium
Dechloromonas
Desulphosporinus
Ferribacter
Uncultured
DNA clone library (total clones 30)
Geobacter
Oxalobacter
Clostridium
Dechloromonas
Desulphosporinus
Ferribacter
Uncultured
y = 0.4788x + 7.4456R2 = 0.3234
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0
% Total Clones cDNA
% T
otal
Clo
nes
DNA
FWB215Slurry ExperimentsSlurry Experiments
Tracer Test / Flush ExperimentTracer Test / Flush Experiment
Timothy D. Scheibe Pacific Northwest National Laboratory, Richland, Washington, USA
Eric E. Roden The University of Alabama, Tuscaloosa, Alabama, USA
Scott C. Brooks Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
John M. Zachara Pacific Northwest National Laboratory, Richland, Washington, USA
CRITICAL ISSUE: How to test hypothesis at the field scale?
We added electron donor and saw U(VI)
decrease…
OK… But WHY?
Hmmm.. .Did they account for the U(VI) coming in from up-gradient sources?
EXPERIMENTAL CONCEPT: Flush Experiment for Mass Transfer Rate Determination
Schematic diagram showing streamlines of injected water (with tracer) in dark blue and diverted streamlines under injection conditions of contaminated water flowing into the study zone from upgradient (red lines with arrows). The light blue circle represents the injection well (i.e., FW215) and dark green circles represent nearby monitoring points (FW212, FW213, FW214). Contours of hydraulic head are indicated by the grey lines.
Accessible porosity within the zone of the aquifer encompassed by the blue streamlines is “flushed” of ambient contamination during the injection event. Any remaining solutes must then be provided from a local source (e.g., desorption and/or mass transfer from
secondary porosity or an non-advective zone)
Simulated (two cases)
Observed
Effect of Desorption KineticsObserved
Simulated
Core/Well DataCore/Well DataPrevious Cores GP01 – Geophysical Well
Installed Feb. 2005
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0 200 400 600
Total Fe (umol/g)
Dep
th B
elow
Top
Bou
ndar
y (f
t)
> 4000
2000-4000
1000-2000
106-1000
53-106
< 53
0.00
0.50
1.00
1.50
2.00
2.50
3.00
0 50 100 150 200 250Total U (umol/g)
Dep
th B
elow
Top
Bou
ndar
y (f
t)
> 4000
2000-4000
1000-2000
106-1000
53-106
< 53
Above: Borehole flowmeter data from well GP-01. Total pumping rate = 2 L/min.
Right: Map of experimental cell showing those wells with bromide breakthrough